Unloader for fluid-compressors.



W. PRELLW 'ELE UNLADEB. FSR FLUD l Patented Feb. 24, 19M

2 SHBXiTS--EHHET l.

APPLICATGN FILED M Y f Mbfmw its downward movement when released by the fluid pressure operated lunger, said spring-actuated mechanism being also-used for exerting the proper tension against the` hollow member 10` of the centrifugal gov-- ernor the branches 11, 12 of which form pivots 13, 14, for the armsv 15, 16, of the weights 17,- 18, of the governor, which arms control the rising and falling movements of the auxiliary valve-operating rod 19, the upper end of which rod is connected to the auxiliary unloader valve 20. A- spring 21 tends to limit the movement of the weights away from each other when the governor is being rotated. Another spring 22 is arranged in position to engage one arm 23 of a rock lever, the other arm 24 of which'is arranged in position to bear upon projections 25 on the movable governor rod 1l) for tending to hold the rod and' thereby the auxiliary 'unloader valve 2()` at the limit of its downward movement and for resisting the upward movementof the rod to the desired extent. The unloader bracket 26 is provided with a cylinder 27 'within which the fluid pressure operated plunger 28 is fitted to rise and fall. This plunger 28 has ab lost motion connection with the `auxiliary unloader valve 20 so that when the plunger 28 is at the limit of its downward movement, the auxiliary valve 20 may be moved to the limits of its movement by the centrifugal governor without al'ecting the movement of the plunger 28. This lost'motion connection -is herein shown as being provided for by having the plunger provided with a downwardly extended shank 29 having a head 30 located within a recess 31 in a hollow cap 32 screwed into the outer end of the auxiliary valve.

The plunger 28 is normallyv held at the limit of its downward movement by the usual weighted lever 33 and interposed pin 3,4. The weighted lever 33 is provided with two contacts 35, 36, the said contacts being arranged to'` alternately contact with the points 37, 38 for throwing the current into the automatic motor starting device 38*, when the Contact 35 engages the contact 37,

for starting the motor; and for shutting oit.

the current from the motor starting device when the contact 36 engages the contact 38. This motor starting device is of the usual Construction where the engagement of one set of contacts will start the device Aand the engagement of another set of contacts will stop the device. The required amount of friction. may be imparted to the lever 33 at its pivotal connection on the unloader bracket 26. l Y The auxiliary valve 20 is fitted to slide in a partition which divides the space beneath the plunger 28 into upper and lower chambers 39, 40 in open communication with each other through one or more vertical holes 41* through said partition and in open communication with the receiver (not shown herein) through the port 39*.

The face of the auxiliary valve20 is provided with two bridge ports 41, 42 and two through ports 43, 44. Three passages 45, 46, 47, lead from the face of the auxiliary valve 20, the passage 46 leading to atmosphere, the passage 45 leading to thespaee -wit'hin the main valve box at one side of the main valve piston 48 and the passage 47 leading to the space at the other side of the said piston 48. The through ports 43, 44, in the auxiliary valve 2O are connected to the chamber 49 between the heads of the main valve piston 48 through passages f The main unloader valve is denoted by 52 and it is provided with two bridge 'ports 53, 54 and the main valve box is provided with two exhaust ports 55, 56, to atmosphere. This box is further provided with ports 57, 58 for the passages leadinor respectively from the intercooler, not sliown herein, through the pipe 59 and from the hack of the low pressure discharge valve 60 through the pipev 6l. The main valve box is further provided with a vort 62 for the passage which leads from t e back of the high pressure discharge valve 63 through the pipe 64. A pipe 65 leads from the receiver, not shown herein', to the space 49 betweenthe heads of the main valve piston 48 for supplying receiver pressure to said space. When the auxiliary valve 20 is at the limit of its downward movement, its bridge port 41 will open communication from the space at one end of the main valve piston 48 to atmosphere through the passages 46, 47, and

its .through port 43 will'open the space at the other end of the piston to receiver pressure through the passages 45, 50. This will move the main valve piston into the posi` tion shown in Figs. 6 and 7 and thereby unload both the high and low pressure dischargevalves by opening the backs of the said valves to atmosphere through the ports 62, 54, 56 and the ports 58, 53, 55, as is common in this type of unloader.

v Vhen the auxiliary valve has been moved to the limit of its upward movement, its bridge port 42 and through port 44 will openv the passages so as to reverse the movement 

